This is a 3-sites, double-blinded, randomized, 2X2 cross-over study aiming to compare effects of milk containing only A2 type beta casein versus milk containing both A1 and A2 beta casein proteins on the gastrointestinal symptoms for the health people who self-reported to be lactose intolerant.
Study sites: Shanghai, Guangzhou, Beijing Eligible subjects were enrolled in the study and randomized into one of the 2 study arms: Sequence A1-A2: Oral consumption of milk containing both A1 and A2 type beta casein at Visit 1 and milk containing only A2 type beta casein at Visit 2; Sequence A2-A1: Oral consumption of milk containing only A2 type beta casein at Visit 1 and milk containing both A1 and A2 type beta casein at Visit 2. Washout period: 2 weeks between Visit 1 and Visit 2
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
TRIPLE
Enrollment
600
Oral consumption of 300 ml of milk containing both A1 and A2 type beta casein at 8:00 a.m. on Visit 1 (after 12-hour fasting) and 300 ml of milk containing only A2 type beta casein at 8:00 a.m. on Visit 2 (after 12-hour fasting).
Oral consumption of 300 ml of milk containing only A2 type beta casein at 8:00 a.m. on Visit 1 (after 12-hour fasting) and 300 ml of milk containing both A1 and A2 type beta casein at 8:00 a.m. on Visit 2 (after 12-hour fasting).
Gastrointestinal Symptom VAS scores at 3 hours
Gastrointestinal symptoms were self-measured by study subjects on a scale from 0 (not at all) to 9 (severe) at 3 hours after product consumption at Visit 1 and Visit 2. Data was analyzed as a repeated measures design using a mixed effects ANOVA with symptom VAS scores at 3-hour as outcome, study product (A1 or A2) and study visit (1 or 2) as fixed effects, and a random subject effect nested within the sequence of study treatment (A1-A2 or A2-A1) , and adjusted for baseline symptom scores. Type III tests of fixed effects were used for testing the effect of study products. Contrast tests were generated to compare means for each product.
Time frame: Three hours after product intervention at each of Visit 1 and Visit 2
The percentage of improvement in gastrointestinal symptoms after drinking A2 versus A1
The improvement in gastrointestinal symptoms after drinking A2 versus A1 were classified into 4 mutually exclusive categories according to the following definition: * No symptom: have no gastrointestinal symptoms after drinking product A2 while having symptoms after drinking product A1. * Significant improvement: still have gastrointestinal symptom after drinking product A2, the reduction of symptom scores \>3 * Slight improvement: still have gastrointestinal symptom after drinking product A2, 1\<=reduction of symptom scores\<=3 * No difference (not improved or worsen): reduction of symptom scores\<=0 The frequency and percentage in each category of improvement for each single gastrointestinal symptom, as well as that for all symptoms, are summarized.
Time frame: 1 hour and 3 hours after product intervention
Urinary galactose concentration
Urinary galactose (U-gal) concentration was measured at baseline and 3-hour of each of Visit 1 and Visit 2. Data was analyzed as a repeated measures design using a mixed effects ANOVA with fixed effects of study product (A1 or A2) and study visit (1 or 2) and a random subject effect nested within the sequence of study treatment (A1-A2 or A2-A1) , and adjusted for baseline symptom scores. Type III tests of fixed effects were used for testing the effect of study products. Contrast tests were generated to compare means for each product. The U-gal measurements over the whole study period (both Visit 1 and Visit 2) for all subjects were also summarized by study product. Product difference was evaluated using one-way ANOVA.
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Time frame: baseline and 3 hours after product intervention of each of Visit 1 and Visit 2
Gastrointestinal Symptom VAS scores at 1 hour
Gastrointestinal symptoms were self-measured by study subjects on a scale from 0 (not at all) to 9 (severe) at 1 hour after product consumption at Visit 1 and Visit 2. Data was analyzed as a repeated measures design using a mixed effects ANOVA with symptom VAS scores at 1-hour as outcome, study product (A1 or A2) and study visit (1 or 2) as fixed effects, and a random subject effect nested within the sequence of study treatment (A1-A2 or A2-A1) , and adjusted for baseline symptom scores. Type III tests of fixed effects were used for testing the effect of study products. Contrast tests were generated to compare means for each product.
Time frame: One hour after product intervention at each of Visit 1 and Visit 2
Change of urinary galactose concentration from baseline at 3 hours <0.27 mmol/L (Yes/No)
Based on the results of urinary galactose test, subjects were classified as lactose malabsorbers if they had an increase in urinary galactose concentration of \<0.27 mmol/L at 3 hours after oral consumption of 15g lactose (corresponding to 300 ml of product A1). And those with an increase in urinary galactose concentration of ≥0.27 mmol/L at 3-hour were classified as lactose absorbers.
Time frame: 3 hours after product intervention of each of Visit 1 and Visit 2